Milling machine



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^ .MILLING MACHINE f' original Filed Aug. 1e. 193'/ v sheets-sheet v Inv/animos Patented oaf 1s, 1940 PATENT OFFICE mums. MACHINE Edward E. Coffin and August L. Krause, Providence, R. I., assignors to Brown and Manufacturing Company,

Rhode Island Sharpe a corporation of orig/msi application August 1s, 1937, serial No.

Divided and this application January 15, 1940,'Serial N0. 313,866

10 Claims.`

- The present invention relates to improvements' in actuating and positioning mechanism for a machine tool support shiftable to effect relative positioning movements of the work and operatingtool.

'I'his invention is a division of applicants copending application Serial No. 159,698, nled August 18, 1937, for Milling machines. and is herein disclosed in a preferred form as embodied in a manufacturing type milling machine having a transversely movable table, a. rotary milling cutter spindle, and a spindle head which is arranged for vertical adjustment toward and away from the table. The machine disclosed in the drawings'is provided with electrical driving and control devices for operating each of the table, spindle and spindle head. j

It is a principal object of the invention to provide a-novel and improved actuating and posi- 2,0 tioning mechanism for a machine tool support which is capable of producing extremely accurate adjustment in the relative operating positions of the work and operating tool.

It is a. further object of the invention to provide 7.25 novel electrical control devices for an adjustable machine tool support which are Well adapted for effecting positioning movements of a milling machine spindle head With certainty and accuracy the operator.

With these and other objects in view, as may Ahereinafter appear, vthe several features of the invention consist in the devices, combinations and arrangementof parts hereinafter described and claimed. which together with the advantages to be obtained thereby will be readily understood by one skilled in the art from the following description taken in" connection with the accompanying drawings, in which Fig. 1 is a view in front VI elevation of a milling machine, only so much of the machine being shown as is believed necessary to illustrate the connection of the present invention therewith; Fig. 2 is a detail plan view of the work table and cutter spindle, illustrating particularly the disposition of the oppositely faced cutters and the work pieces to be engaged thereby; Fig. 3 is a. diagram disclosing one operating cycle of which applicants improved machine is capable; Fig. 4 is an enlarged detail view in front elevation, with a. portion of the casing lbroken away and certain of the parts shown in section to illustrate particularly the electrical control de- 'vices including the upper and lower limit switches for positioning the spindle head; Fig. 5 is a view looking from the left, of the parts shown in Fig.

both automaticallyv and under the control of a. carriage or spindle head |26 which is supported .forming an integral unit with the base |22. The

(01,90-15) 4; Fig. e is 'a detail sectional viw iri'f'rovt levation of one of the limiting switches `for' controlling the vertical movement of the spindle carriage;

Fig. 7 is a perspective view of' the switch larm shown in Fig. 6; Fig. 8 is a. sectional plan view 5 taken on the line 8 8 of Fig. 4, to illustrate particularly the driving connections for imparting vertical movements to the spindle carriage; Fig.

9 is a sectional view take'nvon the line 9-9 of Fig. 8; Figs. 10 and 11 taken together, illustrate 10 the complete wiring diagram cf the machine; Fig.

12 is fan explanatorydiagram to 'illustrate in a simplified form the operating connections illustrated in Figs. 10 and 11; Fig. '13' isaview in front elevation of the machine similar to Fig. 1, Alli but illustrating a dierent set-up' of the table dogs for the milling of two keyways of diiierent levels in a work piece; Fig. 1 4 is a diagram of the'machine operating cycle produced by the setv ting of the table dogs illustrated in Fig. 13: and 20 Fig. 15 is a detail plan view illustrating onel of the table dogs employed for operating the mercurylswitch to short-circuit lower limit switch LSD The machine disclosed in the drawings as em-l bodying in a preferred form the several features of the present invention, is of the general type disclosed in the patent to Bennett and Krause, No. 2,068,840, dated January 26, 1937, and comprises a work table |20 supported for transverse movements'on ways formed on a base |22, and a milling cutter spindle |24 rotatably mounted on for vertical adjustment on a machine column |28 work table of the machine is driven by means of a reversible two-speed electric motor |29 illustrated in Figs. 11 and 12, through mechanical driving connections including a fast-slow clutch which is shiftable to cause the table to be driven from the motor alternatively at a feed or transverse rate. Th'ese driving connections as generally shown in Fig. 10 of the drawings, comprise a. slow feed gear train including the Worm |30 continuously driven from the table,"v motor Ithrough connections, not shown, and worin `gear |32 loosely supported to turnen a hollow driven shaft |34, and a quick traverse gear train comprising the bevel driving gear |36 continuously driven from the table ymotor through connections, not shown, and'gear |38 loosely sleeved onfthe shaft |34. There is alsofrigidly keyed to the shaft |34, a fast-slow clutch member |40, which is shiftable between alternative driving positions Vin which the clutch sleevey |40 and shaft |34 are end by means of a bell-crank |46 and link |48 to 1 the armature |50 of a solenoid |62. A compression spring |54 supported between a stationary member |56 and a collar |58 on the: control shaft |44, tends normally to maintain the clutch member |40 in its position to the left in engagement with the slow feed worm gear |32. The cutter spindle |24 is driven from a reversible electric motor |59 and reduction gearing carried on the head |26 as shown in dotted lines in Fig. 1 of the drawings. Inasmuch as these connections for driving the table and spindle, have been fully described and illustrated in the patent to Bennett and Krause above referredto, and form specifically no part `of the present invention, further illustration thereof is believed unnecessary.

The machine disclosed in the drawings, is provided with automatic means for raising and lowering the spindle |24 and spindle head |28 on the column |28. This mechanism,l as best shown in Figs. 4, 8 and 9, comprises a vertical elevating screw shaft |60 rotatably supported adjacent its upper end in bearings |62 and |64 in an overhanging portion |66 of the column |28, and at its lower end having a screw-threaded engagement with a stationary nut |68 rigidly secured to the spindle head |26. In order that the screw |60 may be supported against endwise movement in the machine, the bearing |64 takes the form of an end thrust bearing which engages with a collar |10 rigidly secured to the elevating screwV shaft |60. The shaft |60 ls power driven to raise and lower the cutter spindle |24 and spindle head |26 by means of an electric motor |12 supported on the column |28. The driving connections from the motor |12 comprise a worm |14 supported on a transversely extending shaft |16 keyed to the armature shaft |18 of the motor |12, and arranged to mesh with a worm gear |80 on an intermediate drive shaft |82 mounted in' suitable bearings |84 in the overhanging portion |66 of the column |28. A gear. |86 also secured to the intermediate drive shaft |82 meshes with 'a gear |88 on the elevating screw shaft 60.

The operation of the electric motor |12 may be controlled automatically as, for example, from the table dogs of the illustrated construction, in

'accordance with a predetermined operating cycle of the machine, or'manually by means of the raising and lowering switch buttons |89, |9I, depending upon the setting of the hand-automatic switch knob 3||| hereinafter more fully to be described. The manual switch buttons |89, |9| may be employed in connection with a measuring device to secure a i'lne manual adjustment of the vertical position of the cutter spindle |24 and the spindle head |26. To this end a dial |90 is supported on the elevating screw shaft |60 which is graduated to measure the amount of the adjustment produced by turning the elevating screw shaft |60 with relation to a stationary marker |92 (see Fig. 9) to the nearest thousandth of an inch. The dial |90 is mounted on a sleeve member |94 supported on the elevating screw shaft |60 between the bearing or bushing |62 and two lock nuts |96 screw-threaded to the shaft |60. The dial |90 is rigidly clamped to the sleeve |94 between a shouldered portion of the sleeve and a `knurled nut |98 screw-threaded thereon. Prior to making a manual adJustment in the vertical position of the spindle head, the nut |98 is backed oil' to release the dial |90 which is then turned to zero position with relation to the marker |92, and again clamped to the elevating screw shaft |60.

The machine illustrated in the drawings, is provided with an electrical control system which is in many respects similar to that illustrated and described in the patent to Bennett and Krause above referred to, including feed and traverse switch control elements operable either manually 'or by means of table dogs to control the direction, rate of travel, and starting and stopping of the table, together with controls operable automatically or manually for starting and stopping and determining the direction ofrotation of the cutter spindle. As in the Bennett and Krause patent above referred to, there is also provided an additional switch control operated by table dogs to cause the table to be driven alternatively at` either of two feeding rates.

In accordance with a principal feature of the present invention,l electrical devices are provided for controlling the operation of the spindle head motor |12, which are constructed and arranged to provide for a more fully automatic operation of the spindle head actuating and positioning mechanism. The electrical devices referred to, include directional starting switch connections for the motor, an upper limit switch and two lower limit switches for accurately stopping the support movement in a plurality of predetermined operative and inoperative positions, an upper safety switch connection, additional manually operable switch connections for controlling the direction and extent of support movement, and a number of selector devices adapting this mechanism for convenient manual control and for automatic operation over a wide range of operating conditions, A number of novel operating cycles in which the vertical movement of the spindle is coordinated with the table and cutter spindle drives, will be herein described in explanation of the electrical controls for the spindle head actuating and positioning mechanisni, and as illustrating the wide range of usefulness of applicants mechanism. It will be understood, however, that features relating to the interlocking control between the spindle head and the work supporting table herein incidentally described, form no part of the present invention, but form the subject-matter of the parent application Serial No. 159,698 above referred to.

As best shown in Fig. 1 of the drawinga'the table operating controls include the manually operable Fast left, Fast right, Feed 1eft,'Feed right, and Stop switch control buttons supported on a control post 2||| mounted on the machine base |22 adjacent the front side of the work supporting table |20, together with corresponding dog actuated control plungers 2|| for operating each of these switches mounted on the rear side of the post-2|0 as generally indicated in dotted lines in Fig. l. The plungers 2|| engage respectively with correspondingly designated table dogs adjustably supported in a T-shaped slot 2| 2 formed on the front side of the table |20. For enabling the table to be driven at either of two desired feed rates, there are also provided at the rear side of the'table, two vertically movable dog actuated plungers 2|4 and 2|6 shown in dotted lines in Fi'g. 1, and arranged to be operated by dogs such as those shown at 2|1, 2|8 and 2|9 LS for high speed or 220 on the rear side of the table. The plungers 2|4 and 2| 6 operate to control the position of the mercury switch illustrated in the electrical diaswitch contact 2-2'|, driven at the relatively the downward erates to close causing the table to` be movement of the plunger 2| opslower feed rate. connectionsl not here shown, for controlling the mercury switch, are fully described and illustrated in the patent to Graves and Bennett No. 2,077,408, dated April 20, 1937, for Machine tools, and form speciiically no part of the present invention, no further description thereof is believed necessary. i

The operation of the spindle motor |59 and cutter spindle |24 is controlled automatically during the operation of thetable in accordance with the setting of a number of spindle control switches-supported on a panel 222 on the machine'column |28 (see Fig. i). These controls as set forth in the captions on the panel 222, provide for alternative continuous i operation of the spindle, and further determine the direction of spindle rotation during table travel in each direction.

The raising and lowering of the spindle head |26 may be controlled automatically in accordance with any one of several operating cycles of the machine, or manually by means o1' control elements supported on a panel 224 on the-machinecolumn |28. These controls include manually operable raising and lowering buttons and a hand-automatic selector control knob, as indicated in the captions on the control panel 224 (see Fig. 1).

'I'he construction and operation of the-electrical connections for controlling the operation 0f the table, the cutter spindle andthe spindle head elevating screw respectively through 'their driving motors, will be briey described in connection with the electrical wiring diagram (Figs. 10 and 11) and the explanatory diagram (Fig. 12) so far as necessary to make clearthe connection therewith of the several new and patentable features of construction and operation of the spindle head actuating and positioning mechanism herein set forth.

The table, spindle, and spindle head motors are driven from a three-phase power line designated as Ll, L2 and L3. The table motor |29.is controlled by a reversing switch having two exciting relays L and R. 'I'he main switch for the table motor .is supported on a panel indicated in dotted lines at 226 (see Fig. of contacts which are controlled by the relay coils L and R respectively to connect the motor and table for right or left hand operation. .The high speed and low speed switch of the table motor is mounted on a second panel indicated at 228 in dotted lines, and comprises two sets of contacts controlled respectively by the relay coils HS or low speed operation of the table motor.

On another panel indicated at 23|) in dotted nes, are carried the main switch contacts for the spindle motor |28 controlled by means of two relay coils SF and SR`for opposite directions of rotation of the motor and spindle driven thereby. It will be noted that the spindle motor control panel 222, and the spindle carriage mofaster feed rate, whereas,-

Inasmuch as the mechanical or intermittent l1), and comprises two sets secondary relay On another panel indicated at 232 in dotted unes (Fig. 1o),

by the left and right quicktraverse buttons, the

hich controls the operation oi' the slow i'eed and solenoid |50, and two additional relays TL| an TRI which are connected in parallel with the ireconnect the motor |12 and cutter spindle |24 for upward or vdownward quick traverse clutch movement. An additional switch controlled by a relay DR is provided for connecting the motor |12 and cutter spindle for an additional increment of downward movement whenit is desired to secure a second finishing cut at a greater d'epth, and during movement oi' the table in a reverse direction. 1

For.controlling the operation of the spindle ing 242, and is normally maintained ina raised so arranged that a downward pressure on the slidably supported in the overhanging portion |66 of the column |28, the plunger. 245 being arranged to operate the lower limit switch LSDI, and the plunger |41 being arranged to operate the lower limit switch LSDZ 248 in the casing |66, and having screw-threaded thereto a tubular member 250 within which is slidably mounted a switch contact plunger or` pin 252. The pin 252 is normally maintained in a fully extended downward position 'with relation to the tubular member 250 in which the enlarged head of the pin 252 engages against a collar 264 screw-threaded into the lower end of the tubular member 250 by means of a` small compression spring 256. The entire plunger unit is held yieldingly in a limiting raised position in which the flanged lower end 258 of the member 256 .engages against the casing |66 by means of a compression spring 268 coiled about the member 250 between a shoulder formed in the bore 248 and the abutting end of the cap 241. A. flat disk 262 screw-threaded to the lower end of the pin 252, is arranged for engagement during the downward movement of the plunger with the actuating pin 244 for the lower limit switch LSD2. Upward movement of the compound plunger 241 to the raised position illustrated in Fig. 4, is arranged to cause the actuation ofthe upper, limit switch LSU through connections' which comprise a switch lever 264` supported on a stationary pivot 266, and having one end thereof arranged to overlie the disk 262. The other end of the switch arm 264 is provided with a spring-pressed plunger 268 which is arranged when the switch arm 264 is rocked in a clockwise direction as viewed in Fig. 4, to engage with the actuating pin for the upper limit switch LSU. A small tension spring 210 connected between the switch arm 264 and the stationary portion of the machine frame, tends to move the switch leverl264 and plunger 268 to a raised position when released by the.down ward movement of the plunger 241.

Inasmuch as the compound plunger 245 for actuating the lower limit switch LSDI is identical in its construction and mode of operation with the plunger 241 above described, no detailed description thereof is believed necessary.

The compound plunger units 245 and 241 above described. are arranged to be acted upon by means of an adjustable stop mechanism which is movable with the spindle head |26 to cause the actuation of the lower limit switches LSDI and LSD2 and the upper limit switch LSU. This stop mechanism comprises a vertical stop rod 212 screw-threaded at its lower end into the spindle head |26 to move therewith, andsldably supported toward its upper end in a bearing -214 formed in the overhanging portion |66 of the column |28. The stop rod 212 has supported thereon a stop bracket 216 which carries two stop pins 218 and 280 arranged for engagement respectively with the compound plungers t245 and 241. In order to permit the replacement of the stop pins 218 and 280, these pins are mounted in a removable block 282 rigidly secured tothe bracket 216 by means of a clamping screw 284. The bracket 216 is rigidly secured in adjusted position on the stop rod 212 by means of a clamping screw 286.

In order to secure a ne adjustment in the position of the stop bracket 216 and stop pins 218 and 288 on the stop rod 212, a second stop bracket 288 is mounted on the stop rod 212, and is connected to the stop bracket 216 by means of an adjusting screw 290 having formed thereon a knurled head 292, and having the oppoammore site ends thereof screw-threaded respectively into the brackets 216 and 286. These screw threads have a slightlydifferent pitch, so that rotation of the adjusting screw 298 after the clamping screw 286 has been-backed off, will operate to produce a ilneladjustment of the stop bracket 216 lengthwise of the stop rod 212. A clamping screw 294 is provided to secure the' bracket 286 rigidly to the stop rod 212.

The operation of applicants mechanism for Acontrolling the operation of the limit switches LSU, LSDI and LSD2 to arrestthe upwardand downward movement of the spindle carriage and cutter spindle in the desired position, may be briefly described as follows:

Assuming that the spindle carriage is in its raised inoperative position as shown in Fig. 4, and that the spindle head motor |12 has been started to move the spindle carriage downwardly, the stop 218 engaging against the plunger 245 will operate to depress the plunger. This downward movement will continue until the plunger engages with and depresses the pin 244 to actuate the limit switch LSDI, thus stopping further downward movement of the carriage. Any overrunning of the spindle head |26 during its downward movement, will be Vtaken care of by the yielding connection within the plunger itselfv which, as previously pointed out is identical in all respects with the plunger 241 above described. When during the subsequent operation of thel machine, the spindle head motor is again rendered operative to continue the downward movement of the spindle carriage for a second cut at a greater depth, the pin 280 engages against and depresses the plunger 241 causing the disk 262 on the plunger 241 to engage with and operate the limit switch LSD2 to again stop the spindle motor. Assuming now that the spindle head motor |12 has been again rendered operative to raise the spindle, the upward movement of the stop rod 212 and stop pins 218, 280 therewith will permit' the compound plungers 245, 241 to rise under the iniiuence of their springs 260 until the flanged disk 262 associated with plunger 241 engages with and turns the switch lever 264 about its pivot 266 to cause the plunger 268 to engage with and operate the upper limit switch LSU to again stop the spindle motor |12.

Figs. l, 2 and 3 of the drawings, illustrate a representative set-up of applicants machine for automatic operation in which successive rough hook milling and finish conventional milling cuts are performed by a milling cutter 29|) at different levels upon a work piece 292 mounted toward the left hand end of the work supporting tablel |20, and in which successive rough hook milling and finish conventional milling cuts are taken by an oppositely faced cutter 294 at different levels upon a work piece 296 supported toward the right hand end of the table |20. In accordance with the set-up of the machine illustrated, each hook milling cut is performed at a relatively faster feed rate, the following finish conventional milling cut at the lower level being performed at a slower rate in order to produce a finely milled surface on the work. from an.intermediate position as shown in Fig. 2, the operator presses the fast-right button, causing the table to move at a quick traverse rate to the right, the milling cutter head |26 being at this time in the raised inoperative position illustrated in Fig. 4. As the cutter 290 approaches the work piece 292, the feed dog 298 actuates the feed right Assuming that the table is started the relatively faster feed rate. The operation of` switch which operates through the electrical connections hereinafter more fully to be described, to stop the table motor'and to start the spindle cutter head |26 feeding down. As the cutter 290 When the table has moved to the right a suilicient distance to bring the cutter 290 against the shouldered end of the work piece 292, the reversing feed dog 299 actuates the feedleft switch to reverse the direction of table travel.

'I'he actuation of this switch operates to again start the milling cutter head 26 feeding down, until arrested by the opening of the second lower limit switch ISDZ through the operation of plunger 245 when contacted by the stopl pin 280. During this down movement of the spindle head |26, the table is held stationary. The operation of the second lower limit switch LSD2 operates to start the table moving to the left, while the cutter spindle |24 continues to rotate in a counterclockwise direction for the performance-of the second finish conventional milling cut at the lower level. At the instant of reversal, the slow feed dog 2|1 on the rear side of the table, contacts with the slow feed plunger 2|6 to cause the table motor to be driven during the second lmilling operation at the slower feed rate.

At the completion of on the work piece 292, is actuated by contact with a lfast left dog 360 which operates first to stop the table |20 and spindle rotation, and then to start the milling cutter spindle head |26 feeding'upwardly to its inoperative position in which the flanged disk 26.2 of the plunger 241 acting on the switch lever 264, causes the actuation of the upper limit switch LSU, thus arresting the upward movement of the spindle head |26. The actuation of the upper limit switch LSU also operates to start the table moving at quick traverse to the left. During this traverse movement of the table, the fast feed dog 2|8 again contacts with the fast feed plunger 2| 4, so that the table motor switch control will automatically be set for operation of the table at the finish milling cut the machine to cause successive rough hook milling and finish conventional milling cuts to be performed by the cutter 294 on the work piece 296 is controlled through the agency of feed left dog 302, feed reversing dog 904 and the fast traverse right dog 306, and through the agency of slow feed dog 2|9 acting on the slow feed plunger 2|6, the operation of the machine as controlled by these dogs being identical in every respect with that described in connection with the milling of the work piece 29.2 at the left hand end of the table.

The operation of the electrical connections to cause the machine toop'erate in accordance with the automatic cycle above described, may be briefly described as follows:

It is assumed that the spindle head raising and lower hand-automatic switch 3|0 is set for automatic position, the spindle intermittent-continuton, relays TR, TRI

the table fast left switch -a brake solenoid 3|2 ous switch is set for intermittent operation, and that the spindle direction table left and table right switches are set respectively for clockwise operation of the spindle .during'the travel of the table to the left, and for'counterclockwise operation of the spindle during the travel of the table to the right. It may be assumedfurther that the adjustment and relative length of the stop pins 218 and 280 has been chosen tocause the lspindle head |26 and cutter supportedthereby, to move correctly to each of the two rough and finish milling positions.

When the operator presses the fast right butand RR are energized and held in by holding contacts RR |3-|2, 'I'R |2-40 and 'IRl 40-I5. The closing'of contact the table motor to start driving the table to the right. At the same time contacts TR. 23-2l and TR 2|'-20 close energizing contacter RC assuming LSU 68-3 is closed. Contact TRI 63--6I has already closed so the img traverse solenoid is energized, thereby placing the table inl fast traverse right. The spindle motor is prevented from starting because contacts lRC 2-30 and TRI 2-29'are held open. 'f

It will readily be seen from the `foregoing description, that the upper limit switch ISU operates as a safety device to prevent thel starting of the table at quick traverse until the spindle cutter head |26'has been fully raised to its upper position. Furthermore, inasmuch as the LSU upper limit switch contact 683 remains closed against the pressure of the spring 210 (see Fig. 4) only while the plunger 2411s in its fully retracted position, any movement downwardly from its fully raised position, must immediately operate to de-energize RC,` and thus stop further quick traverse As the cutter spindle |24 approaches thework piece 292, the feed dog 298` actuatesthe' feed right switch, closing contact 2--I2 and opening contact |5-I6, which de-energizes the TR and TRI relays, leaving RR` energized. vTl't1l--1Il closes, Aenergizing contactar D which starts the, spindle head motor feeding the spindle head down. At the same time, contacts D 2-59 and energizes contactor R which causes of the cutter spindle operation of the table.

D 2-5I open, thereby disconnecting the table` motor and allowing it to stop by plugging., By this time the spindle |24 has started to rotate in a counterclockwise direction through thefclosing of contacts RC 2-30 and TRI 2--29, which operate to complete the circuit through the spindie direction table right switch contacts3I-12 to energize the spindle motor contactor SR. When the spindle rough hook milling cut position, lower limit switch LSDI is actuated through the operation of plunger 245 contacted by stop pin 218. The opening of the LSDI contact 10-46 operates to de-energize the D, thereby stopping further downward movement of the spindle head 26.

In order to provide for the substantiallyinstantaneous stopping of the spindle head, an electrically operated ture shaft |18 of the spindle head motor |12 to arrest further rotation of the motor. The operation of the brake is controlled by means of vshown in Fig.` 10, which operates to apply the brake whenever the motor is de-energized. The braking action thus obtained, is of particular advantage in connection with the spindle headV vertical movement to prehead has been fed down to the friction brake, not specificallyxillustrated is arranged to act on the armavat 6 vent vertical movement oi the spindle head during the perfomance of milling cuts on the work.

When the contactor D is de-energized as above set forth, contact D 2-5I closes, energizing contactor R, so that the table '.arts feeding to the right, causing the cutter 299 to perform a rough hook milling cut on the work piece 292. The engagement of the fast feed dog 2|8 with the fast feed plunger 2 I4 during the previous quick traverse of the table to the right, has in the meantime shifted the mercury switch from the position shown in Fig. 12, to open the mercury switch contact 2-28, and to close the mercury switch contact 221, so that contactor HS is energized to drive the table motor at the faster feed rate.

When this roughing cut on the work piece 292 is completed, the table feed reversing dog 299 operates the feed left switch. closing contact 2-1 and opening contact Ill-l I, which de-energizes contactor RR and which in turn energizes contactor LR. Due to the overlapping action of relays LR and RR, contacts `LR 10-48 and R 48-49 are closed simultaneously for a space of time lon'g enough to allow relay DR to be energized. The contactor DR is then held in through the holding contact DR 10-64. Contact DR 10-46 short-circuits lower limit switch LSDI which is now open due to the operation of the switch plunger 241, and allows contactor D to energize, thereby starting the spindle head feeding down to a second level which is determined by the engagement of the stop pin 280 with plunger 241 to open the lower limit switch LSD2. During this downward feeding movement of the spindle head |26, the table remains stopped due to the opening of contact D 2-5I. The opening of the switch LSD2 when the spindle head |26 reaches the lower level, causes contact D 2-5I to close, establishing a circuit through contact LR I9|8 to energize contactor L, thereby starting the table motor to feed the table to the left. The cutter spindle |24 is in the meantime kept rotating in a. counterclockwise direction through the operation of the holding circuit contactSR 35-3I. At the moment of reversal of the table, the slow feed dog 2 l1 engages with the slow feed plunger 2I6 to reverse' the mercury switch to the position shown in Fig. 12, opening the mercury switch contact 2-21, and closing contact 2-28, so that the relay HS is de-energized, and LS is energized to drive the table motor |29 at the slow feed rate.

Upon the completion of the iinishing cut, the fast traverse left dog 300 operates the fast left switch, closing contact 2I0 to energize TL and TLI, which areheld in by lthe closing of the holding circuit contacts TL 1-39 and TLI 99-I9. As TLI 15-11 closes, it energizes contactor U through the upper limit switch LSU contact 61-3. Contactor U starts the spindle head motor |12 which drives the spindle head |28 upwardly until the upper limit switch LSU is actuated by the upward movement of switch plunger 241 acting through connections above described including the switch actuating lever 264 (see Fig. 4). During the operation of raising the spindle head, contact U 5I-I9 remains open, thereby stopping the table. The actuation of the upper limit switch LSU opens contact 61-3, thus de-energizing contactor U and stopping further upward movement of the spindle head |26. Contact U 5|I9 now closes, and the upper limit contact 68-3 is closed through the operation of this switch as above described.

Since TL 22-2I and TL 2I-20 are already closed, the circuit is completed to energize contactor RC, thus shifting the table to quick traverse operation. Contactor L is energized at the same time, thereby starting the table motor to drive the table to the left infast traverse. The opening of RC contact 2-30 operates to cleenergize contactor SR to stop the spindle. at the same time disconnecting the SR interlock or holding contact 35-3 I. It will readily be seen that. when the table is again slowed to a feed rate travelling to the left, that the starting of the spindle motor |59 will be controlled by the position of 'the spindle direction tame left switch. with the operating cycle herein set forth, this switch is set to cause the circuit to be closed through the switch contact 35-14 to energize contactor SF to effet a clockwise rotation of the cutter spindle I2 Inasmuch as the operation of the electrical n controls to cause the cutter 294 to perform successive rough hook milling and finish conventional milling cuts on the work piece 296 located toward the right hand end of the table, is similar in all respects to the operation above described in connection with the milling of work piece 292 at the left hand end of the table, it is believed that no further detailed description thereof is necessary.

While the spindle raising and lowering mechanism above described, is of particular advantage for automatic operation in accordance with a variety of table operating cycles of which the above is an example, it will readily be seen that the electrical connections employed for raising Il and lowering the spindle head, are well adapted to be controlled directly by the operator, who has merely to press either of the control buttons on the panel 224 designated as Raise and Lower to move the spindle directly to the desired position. The shifting of the hand automatic switch 3|0 on the panel 224 to hand position, operates through the opening of switch contact 2-15 to render the raising and lowering oi the spindle head |26 independent of the feed and traverse switch connections controlling the operation of the table. It will readily be seen from an lnspection of Fig. 12 of the draw-ings, that the closingl of the spindle lower control contact 2-46, operates directly to energize the contactor D to move the spindle head down. This downward movement is limited by the operation of the lower limit switch LSD2 which, therefore, operates under these conditions as a safety lower limit switch. The shifting of the switch 3I0 to handl position, operates also to close switch contact 61-68, this rendering the spindle Raise control button operative to move the spindle head upwardly independently of the position of the upper limit switch LSU. The closing of switch contact 61-69 has the further eect of permitting the quick traverse contactor RC to be energized for either position of upper limit switch ISU, so that the table can be moved at quick traverse independently of whether the spindle head is in its raised or lower position.

In order to prevent excessive upward movement of the spindle head with consequent damage to the machine, an upper limit safety'switch is provided designated in dotted lines at 359 in Figs. 4 and 5. This switch which may be similar in its general construction and mode of operation to the limit switch illustrated in Figs. 6 and '7, is actuated by means of a plunger 352 slidably mounted in the machine column |28, and arranged. at one. end to engage within a slot in the stop rod 212. ment of they spindle headk |26 will cause the plunger 352 to rideout of the cammedlower end of the slot 354, 'and open the upper safety switch contact 66-61 (see Figs. 11 and 12). In order to prevent any possibility of an excessive down.- ward movement of the spindle head |26, a` collar 358 is rigidlysecured to the upper'end'of the stop rod 212 which serves to limit the adjustmentk of the stop brackets 216 and 288 upwardly on the stop rod 212.

The automatic control devices for applicants machine above described including the mechanism for raising and lowering the spindle head, are well adapted also forxautomatic operation in accordance with an. operating cycle in which aV cutter spindle is brought to one level for the performance of one milling operation, is raised for a quick traverse movement of the table, and is again lowered to a second level for the performance of a second milling operation subsequent to which the cutter spindle is raised, and the work table returned at quick traverse to starting position. Figs. 13 and 14 illustrate a set-up of the machine for the performance'of an operation of this type, in which two keyways 366 and 362 areto be cut in -a motor' shaft 364 suitably mounted on the work table |20. y

In accordance with the set-up illustratedV in` these views, it is assumed that two actuating pins 218 and 280 (see Fig. 5) have been chosen, which are of the proper relative length, so that the pin 218 will engage with its plunger 245 to open the lower limit switch LSDI as the milling cutter 365 (see Fig. 13) reaches the rst operating level, and the pin 280 will engage with its plunger 241 to open the lower limit switch LSD2 as the milling cutter 365 reaches the second or lower operating level. In order to enable the head raising and lowering devices for the machine to operate in accordance with an operating cycle of this description, in which the cutter spindle |24 is lowered directly from its raised position; to each of two work engaging positions at diiferent levels, it has been found necessary in lowering` the spindle head to the lower operating position, to provide means which maybe rendered operative .to short-circuit the lower limit switch LSDI, so

that the spindle head may be permitted to continue its downward movement to the lower work. engaging position as determined by the operation of the lower limit switch LSD2.

' In the preferred construction. illustrated, the

short-circuiting of the lower limit switch contact 1li-46, is accomplished by means of a mercury switch 366 which is readily controlled by means of the dogs 368 and 310 adiustably supported in the T-shaped slot 22|) formed in the rear side of' the table |26. These dogs are arranged to control the position of two plungers 312 and 314 supported in parallel relation to and to the rear` of the fast-slow plungers 2|4 and 2| 6 on a rela.- tively stationary portion of the machine. The plungers 312 and 314 are connected by a pinion 315 and rock shaft 316 to the. mercury switch 366, so that the depressing of` the plunger 312 will operate to close the mercury switch 366, and at the same time to raise the plunger 314, and depressing of the plunger 314 will operate to open the mercury switch.366 and at the same time to 'raise the plunger 312.

The operation of the machine in` accordance with the set-up illustrated in Figs. 13 and 14, for

An excessive upward move-` A beneaththe. cutter |24,

they cuttingl of` the two keyways 360f and 362, may be briefly` described vas follows:

Starting with the table in its positiony at the extremeleft, the operatorv presses they fastfrightv button to move the table at aquick traverse rate to the right. Asvthe work piece |34 is moved the feed dog 311 presses the feed-right button operating yas above described, to stop the tabley and to start the spindle head |26 moving down. In. the meantime, the dog 310 will haveengaged with and moved the plunger 312 downwardly to closev the mercury switch 366, and thus to short-circuit the lower limit switch LSDI. This downward movement therefore is not aected. by the opening of'LSDI contact 10-46 as the pin 218 engages and depresses the switch actuating plunger 245, but continues until the pin 28|)v has contacted with the switch plunger 241 to openthe lower limit switch LSD2, thus de-energizing the coils D and DR to stop the head motor |12, and starting the movement of the table at feed rate to mill the keyway 362i At the end of this milling operation, the traverse right dog 318 engages the fast-right button, causing the table again to stop, and starting the spindle. head |26 moving upwardly. Upward movement of the spindle head |26 continues until the-actuating pin 218 (see Fig. 4:) has moved -out of engagement with the plungerl 245, thus permitting the upper limit switch LSU to be opened by the operation of the switch actuating lever 264, which causes the spindle motor |12 to stop and the table to start moving at the. quick traverse rate to the right. During this traverse movement of the table, the dog 368vengages with and depresses the plunger 314; moving the mercury switch 366 to open position,-and` this breaking the short-circuit around` the lower limit switch LSDI. The continued movement of the table to the right, now causes the feed dog 380 to engage the feed right plunger, again stopping' the table and causing the spindle |26 to start moving down. This downward,` movement con,- tinues'until arrested by engagement of'y the pin 218 with the switch operating plunger 245 which vacts t'o open4 the lower limit switch LSDI. With thev mercury switch 366 in open position, the opening of LSDI contact 10-46 operates,` to deenergize D to stop the head motor |12 and to start the table moving at the feed rate to the right for the milling of thekeyway 36|). At the completion of this milling operation, the fastleft dog. 382 contacts with.v the `fast-left button,

operating to stop the table and to start the to start the returnv movement ofy the table. at n quick traverse rate to the left. This movement of the table continues until arrested by the engagement of a stop dog 384k with the machine' stop button 386 which operates to stop the machine-in its original starting position.

It will be understood that` the inventionv is notv limited to the specific embodiment shown, and. that variousdeviations may be made therefrom without departing fromk the spirit andl 4scope of. the appended claims.

What is claimed is:

l. In a machine tool having a support shiftable between operative and inoperative positions.

driving and positioningmechanlsm for said support comprising driving means operable to move the support alternatively in opposite directions toward one or another of said positions, and electrical control means for said support including a limit switch actuable by movement of the support in one direction to stop the support in inoperative position, a plurality of limit switches successively actuable by movement of the support in the opposite direction to stop the support in a series of operating positions, electrical connections controlled by each of said limit switches for stopping the support, and means for controlling said electrical connections to render a selected limit switch inoperative to stop the support.

2. In a machine tool having a support shiftable between operative and inoperative positions, driving and positioning mechanism for said support comprising driving means operable to move the support alternatively in opposite directions toward one or anotherof said positions, and electrical control means for said support including directional starting switch connections and directional relay switches energized thereby for starting support movement alternatively toward one or another of said positions, a limit switch actuable by movement of the support in one direction to de-energize the associated relay switch for stopping the support in inoperative position, a

plurality of limit switches successively actuable by movement of the support in the opposite direction to de-energize the associated relay switch for stopping support movement in each of a series of operating positions, and a shunt connection actuable to render one of said limit switches inoperative to stop the support.

3.' In a machine tool having a support shiftable between operative and inoperative positions, driving and positioning mechanism for said support comprising driving means operable to move the support alternatively in opposite directions toward one or another of said positions, and electrical control means for said support including directional starting switch connectionsfor the support, a limit switch and a safety switch successively actuable by movement of the support toward inoperative position for stopping the support, a plurality of limit switches successively actuable by movement of the support toward operative position for stopping the support, elec'- trlcal connections controlled by each of said limit switches for stopping the support, additional manually operable directional starting and stopping switch connections for the support, and a selector device operable to render the inoperative position limit stop switchv and the rst of said successively actuated operative position limit switches operative and inoperative to stop the support.

4. In a machine tool having a support shiftable between operative and inoperative positions, driving and positioning mechanism for said support comprising driving means operable to move the support alternatively toward one or another of said positions, and electrical control means for said support including directional starting switch connections for the support, limit switches and electrical connections controlled thereby operative to stop movement of the spindle support in each direction, including a plurality of limit switches individually actuable for stopping the support in a plurality of operative positions, means for controlling said electrical connections to render a selected limit switch inoperative to stop the support, and actuating connections for said limit switches controlled by movement of the support comprising for each operative -position limit switch, an actuating member movable with the support vand adjustable thereon, and a switch contactmember arranged to be engaged by said actuating member for actuating the associated operating position limit switch, said actuating connections further including connections yieldable to permit overrun of the support with relation to each of said operative position limit switches.

5. In a machine tool having a support shiftable between operative and inoperative positions, driving and positioning mechanism for said support comprising driving means operable to move the support alternatively toward one or another of said positions, and electrical control means for said support including directional starting switch connections for the support, limit switches operative to stop movement of the spindle support in alternative operative and inoperative positions, and actuating connections for said limit switches controlled by movement of the spindle support comprising an actuating member movable with the support, a switch contact element shiftable in opposite directions for alternatively actuating said limit switches, and means yieldingly supporting said switch contact element in actuating position with relation to the inoperative position limit switch and arranged to permit movement of said switch contact element by said switch actuating member into actuating position with relation to said operative position limit switch upon movement of the support toward operative position, said actuating. connections further including a connection yieldable to permit overrun of the support with relation to said operative position limit switch. Y

6. In a machine tool having a support shiftable between operative and inoperative positions, driving and positioning mechanism for said support comprising driving means operable to move the support alternatively in opposite directions toward one or another of said positions, and electrical control means for said support including directional starting switch connections and directional relay switches energized thereby for starting support movement alternatively toward one or another of said positions, de-energize the associated relay switch for stopping the support in inoperative position, a limit switch to de-energize the associated relay switch for stopping the support in operative position, and actuating connections for said limit switches controlled by movement of the spindle support comprising an actuating member movable with the support, a switch contact element shiftable in opposite directions for alternatively actuating said limit switches, and means yieldingly supporting said switch contact element in actuating position with relation to the inoperative position limit switch and arranged to' permit movement of said switch contact element by said switch actuating member into actuating position with relation to said operative position limit switch upon movement oi the support toward operative position.

7. In a milling machine having a work support, a rotary milling cutter spindle, and a spindle support movable toward and away from the work support between raised non-work engaging and low work engaging positions, the combination of electrical driving and control means for the spindle support including a reversible electric motor, switch connections loperative for driving the motor to start the spindle support moving from one to the other of said positions, upper and lower limit switches operative to stop the spindle supa limit switch actuabl; to'

relatively movable plunger members and spring member for actuating the upper limit switch.

9. In a machine tool having a support shiftable the mst-mentioned limit stop switch operative and inoperative to stop the support. 

